1. Field of the Invention
This invention relates generally to a drum type washing machine provided with a rotating tub rotatable about a horizontal axis, and more particularly to such a drum type washing machine in which the rotating tub is directly rotated by an electric motor.
2. Description of the Prior Art
There have conventionally been provided drum type washing machines comprising an outer cabinet, a water tub elastically mounted on a plurality of suspension mechanisms in the cabinet, and a rotating tub mounted in the water tub so as to be rotatable about a horizontal axis. Bearings are provided in the rear of the water tub to support a shaft of the rotating tub. The shaft has a rear end on which a driven pulley is mounted. An electric motor is disposed below the water tub and has a shaft on which a driving pulley is mounted. A transmission belt extends between the driving and driven pulleys. Upon rotation of the shaft of the motor, torque is transmitted through the driving pulley and the belt to the driven pulley so that the rotating tub is rotated.
However, provision of the above-described belt transmission mechanism including the driving and driven pulleys and the transmission belt complicates the construction of the washing machine and accordingly increases a manufacturing cost. Further, the driving and driven pulleys and the transmission belt produce vibration or oscillation during transmission of the motor torque. A high speed rotation of the motor particularly causes the transmission belt to slip such that the belt swings. The swinging of the belt increases an amount of vibration produced in the belt transmission mechanism, resulting in production of loud noise.
To solve the above-described problems, Japanese Patent Publication No. 10-201993 (1998) discloses a drum type washing machine comprising an electric motor mounted on a rear wall of the water tub so that the shaft of the rotating tub is directly rotated by the motor. Since no belt transmission mechanism is necessitated in the disclosed washing machine, the construction thereof can be simplified, and the vibration and noise can be reduced. The motor is disposed in a space in the rear of the water tub, in which space the driven pulley and the transmission belt are formerly disposed. In the disclosed washing machine, the motor would collide against the rear wall of the cabinet to be broken when the water tub is caused to swing during drive of the motor to be inclined rearward. Accordingly, the motor needs to be disposed so as to be sufficiently spaced away from the cabinet for the purpose of avoidance of collision against the rear wall of the cabinet. This requires a large space in the rear of the wash tub and accordingly increases a depth of the cabinet.
Furthermore, the drum type washing machine is conventionally installed on a waterproof pan. Sizes of the waterproof pans are standardized according to the sizes of the drum type washing machines. Accordingly, when the depth of the cabinet is increased as described above, the standardized waterproof pans cannot be used.
Therefore, an object of the present invention is to provide a drum type washing machine in which an increase in the depth of the cabinet can be prevented or at least restrained as the result of disposition of the motor on the rear of the water tub.
The present invention provides a drum type washing machine comprising an outer cabinet having a rear wall, a water tub elastically mounted in the cabinet and having a rear wall, a drum type rotating tub provided in the water tub so as to be rotatable about a horizontal axis, and an electric motor provided on the rear wall of the water tub to directly drive the rotating tub, a fixed portion prevented from swinging when the motor is driven, and a contact portion coming into contact with the fixed portion earlier than the motor when the motor is driven such that the water tub swings, the contact portion being provided on the water tub or a member fixed to the water tub except the motor, wherein a distance between a portion of the rear wall of the water tub on which the motor is provided and the rear wall of the cabinet is larger than a distance between another portion of the rear wall of the water tub and the rear wall of the cabinet.
According to the above-described construction, the depth of a portion of the cabinet on which the motor is not disposed can be prevented from being increased while a space for the motor is ensured between the rear wall of the water tub and the cabinet. Further, breakage of the motor can be prevented or at least restrained even if the water tub swings.
The portion of the rear wall of the water tub on which the motor is provided is preferable formed into the shape of a recess. At least a part of the motor is located in the recess of the rear wall of the water tub, so that the rear wall of the cabinet can be brought close to the rear wall of the water tub. Consequently, the depth of the cabinet can be reduced.
The motor preferably comprises an outer rotor type motor. In order that the same torque may be obtained from an inner rotor type motor as from an outer rotor type motor having an outer diameter equal to one of the inner rotor type motor, an axial dimension of the inner rotor type motor needs to become larger than one of the outer rotor type motor. More specifically, since the outer rotor type motor is employed in the above-described construction, the axial dimension of the motor can be reduced. Consequently, the disposition of the motor on the rear wall of the water tub can reduce the depth of the cabinet.
The drum type washing machine preferably further comprises a fixed portion prevented from swinging when the motor is driven and a contact portion coming into contact with the fixed portion earlier than the motor when the motor is driven such that the water tub swings, the contact portion being provided on the water tub or a member fixed to the water tub except the motor. The breakage of the motor can be prevented or at least restrained even if the water tub swings.
The drum type washing machine preferably further comprises a rotational shaft connecting the rotating tub and the motor to each other and a bearing supporting the rotational shaft. In this washing machine, the bearing has a portion located inside a stator of the motor. Since an inner space of the stator is utilized for the provision of the bearing, an increase in the depth of the cabinet can further be prevented.
The rear wall of the cabinet preferably includes a portion opposed to the motor and formed with a vent hole. Since air flows through the vent hole between the interior and the exterior of the cabinet, heat dissipation from the motor can be improved.
The motor preferably includes a rotor provided with a plurality of blowing blades for a cooling operation. Since air flows around the motor by the blowing action of the blades, the heat dissipation can be improved.
The rear wall of the cabinet preferably has an opening, and the washing machine further comprises a back panel detachably attached to the cabinet so as to close the opening. The back panel includes a portion opposed to the motor and formed with an outwardly protruding convexity. At least a part of the motor is disposed in the convexity such that the rear wall of the cabinet can accordingly be positioned forward. Consequently, the increase in the depth of the cabinet can be prevented or at least restrained.
The drum type washing machine preferably further comprises a unit configured to heat provided on a lower portion of the water tub for heating water reserved in the water tub and a hole formed in a lower portion or a side of the convexity of the back panel so as to communicate with an interior and an exterior of the cabinet. Since air in the cabinet heated by the unit is discharged through the hole outside the cabinet, the convexity can be prevented from being filled with hot air and accordingly, the motor can be prevented from being adversely affected by the heat. Further, since the hole is located in the lower portion or the side of the convexity of the back panel, water can be prevented from entering the cabinet through the hole when the water splashes on the convexity.
The motor preferably includes a portion located in the convexity. Consequently, the depth of the cabinet can be reduced.
The back panel is preferably pressed so that the convexity is tapered and the convexity has a hole formed in a lower portion or a side of a peripheral wall thereof so as to communicate with an interior and an exterior of the cabinet. Since the convexity is formed integrally with the back panel, the back panel has no joints. Further, since the convexity is tapered, air tends to easily flow along an inner face of the convexity such that hot air can be prevented from filling the interior of the convexity.
The hole is preferably provided with a louver. Consequently, water or foreign matters can be prevented from entering the cabinet through the hole, and an amount of noise produced by the motor and leaking from the hole can be reduced.
A washing machine is usually installed on a waterproof pan. The waterproof pan for automatic washing machines such as drum type washing machines has a standard size of 540 mmxc3x97540 mm. In view of the circumstances, the cabinet preferably includes a lower portion having a length set at or below 540 mm. Even if the depth of the cabinet is increased as the result of disposition of the motor on the rear wall of the water tub, the washing machine can be installed on the standardized waterproof pan.